Solve for $x$ and $y$ using elimination. ${-4x-3y = -39}$ ${5x+5y = 60}$
Explanation: We can eliminate $y$ by adding the equations together when the $y$ coefficients have opposite signs. Multiply the top equation by $5$ and the bottom equation by $3$ ${-20x-15y = -195}$ $15x+15y = 180$ Add the top and bottom equations together. $-5x = -15$ $\dfrac{-5x}{{-5}} = \dfrac{-15}{{-5}}$ ${x = 3}$ Now that you know ${x = 3}$ , plug it back into $\thinspace {-4x-3y = -39}\thinspace$ to find $y$ ${-4}{(3)}{ - 3y = -39}$ $-12-3y = -39$ $-12{+12} - 3y = -39{+12}$ $-3y = -27$ $\dfrac{-3y}{{-3}} = \dfrac{-27}{{-3}}$ ${y = 9}$ You can also plug ${x = 3}$ into $\thinspace {5x+5y = 60}\thinspace$ and get the same answer for $y$ : ${5}{(3)}{ + 5y = 60}$ ${y = 9}$